Muffler



Oct. 1, 1935. QA G. NOBLITT ET AL MUFFLER 2 Sheets-Sheet 2` Filed Aug. 3, 1951 fr' 'Z il 1 Lui m, m W

Qumrmhfogurr ,ERQL Qoov'H HND EDMuNg LQDLoW,

Patented Oct. 1, 1935 UNITED STATES Mun-LER Quintin G. Noblitt, Earl C. Booth, and Edmund Ludlow, Indianapolis, Ind., assignors to Noblitt- Sparks Industries, Inc., indianapolis, Ind., a

corporation of Indiana Application August 3, 1931, Serial No. 554,722

12 Claims.

Our invention is concerned with silencers for silencing the sound of flowing gases, particularly where such gases are subjected to abrupt; changes in pressure as are'the exhaust gases discharged from the cylinders of an internal combustion engine. It is our object to produce a silencer or muffler which will adequately silence the exhaust gases and which will perform this function without imposing a substantial back-pressure on the flowing gases. A further object of our invention is to produce a muffler which can be simply and economically .constructed of ksheetmetal parts. Still another object of our invention is to produce a muffler of a type which, with l5 structural variations of a simple character, can be made suitable for use with engines of widely varying characteristics.

In carrying out' Aour invention we form the muffler with an exterior casing and an inner tube,

the latter receiving the gases at one end and discharging them at the other and being unrestricted throughout its length. t The tubeis provided with a multiplicity of openings providing at each of a series of longitudinally spaced points rev stricted communication between the interior of the tube and the space surrounding it. The space within the casing and surrounding the tube is divided into a series of chambers by means oi.

partitions located at longitudinally spaced points along the muffler. The muffler is preferably formed of two similar halves each of which is conical in form, the large ends of the conical halveslbeing joined together to form a unitary casing. y

The accompanying drawings illustrate the invention: Fig. 1 is a longitudinal section through one form of muffler embodying our invention;

Fig. ilV is a section similar to Fig. l, but on an enlarged scale, on the line 2-2 of Fig. 3; Fig. 3

is a transverse section on the line 3-3 of Fig. 1,

Fig. 4 is a fragmental isometric view showing one end of the inner tube; Fig. 5 is a fragmental plan showing a portion of one of the pieces which make up the inner tube; Fig. 6 is a fragmental 'isometric view illustrating the construction of the ferrule by which the inner Atube is secured to the central partition; Figs. 'I and 8 are sections similar to Fig. 1 showing modified arrangements;

Fig. 9 is a iragmental section similar to Fig. 7,

but on an enlarged scale; and Fig. 10 is a. fragmental longitudinal section showing the construction at one end of the muiiler.

In the muffler illustrated in Figs. 1 and l2, the

outer muffler casing is formed ol.' two conical halves I5 joined together at their bases. 'I'he inner tube previously referred to is preferably also formed of two halves IS each of which extends from one end of the muiller to a central partition I1 that is disposed between the two casing-halves I5 and divides the space surroundt ing the tube I6 into two parts.

In the muiller shown in Fig. 1, the two halves I5 of the casing are not right-angle cones; but instead are oblique to such an extent that the two halves of the inner tube I6 may be secured l0 at one side of the casing in substantial alinement with each other. As will be pointed out hereinafter, this form of muiiler casing has certain advantages which make it desirable, although it is not necessary to our invention in its l5 broad aspects.

As is clear from Fig. 4, each half I 6 of the inner. tube is conveniently formed of .two sheet-metal stampings each formed in ,generally semi-cylindrical shape and "provided at its longitudinal 20 edges with flanges I8. 'Ihe flanges on the two tube-parts may be secured together as by spotwelding to form a complete tube-half. lAt a point circumferentially'intermediate the flanges I 8, each tube-part is formed with a longitudinally 25 extending. ridge I9. The openings which aiTord restricted communication between the interior of the tube and the space surrounding it are preferably formed by providing each tube-part lwith a series of circumlerentially extending slits which 30 extend between the ridge I9 and each of the flanges I8, the material at one side of each oi' such slits being displaced radially as `indicated at 2l, to provide an opening 22. This radial displacement of the tube-material at one side of 35 each of the slits may be either inward or outward, but we prefer to displace the material outward, as such displacement does not decrease the effective interior cross-sectional area of the tube.

The ridge I9 is provided on the lower part ol 40 the inner-tube for the purpose of affording a surface which may contact with the interior of the muiller casing I5 and be secured thereto as by y spot-welding. Aside from its stiiifening e'ect, the ridge I9 on the upper part of the inner tube has 45 no function and is not necessary; but it is provided in order that both tube-parts may be the same and the cost of production thus decreased.

At each end of the muiller casing, one of the tube-halves I6 fits closely within it, the anges 5: I8 being trimmed diagonally, as is clear from Fig. 10. At its inner end, each of the tube-halves I6 is received within a ierrule 25 which is notched at angularly spaced points to provide for the anges I8 and the ridges I9 on the tube. The 55 ferrule Il has a ange 2i which may be secured to the partition I1 as by spot-welding.

Between the center partition I'I and each end of the muiiier there are one or more auxiliary partitions Il, shown in the drawings as three in number, which serve to divide each half of the casing into separate chambers. The partitions Il are preferably arranged to provide restricted communication between adjacent chambers, as by providing each of them with an opening which receives the tube I0, such opening being slightly larger than the tube to provide an annular passage 2l (Fig. 2). The openings provided in the partitions Il by the passages 29 are not essential, but we find that their presence has a tendency to inhibit the production of secondary noises. The partitions 28 may be located approximately as indicated in the drawings so that the chambers into which they divide the interior of the mutlier are of progressively increasing volume toward the center of the muilier.

In use, the muiiler is connected at one end to the pipe through which exhaust gases are led from the engine, and at the other end to a tailpipe, if such a tail-pipe is desired.` The gases entering the mumer enter the tube I6, which is uninterrupted from one end of the mumer to the other. The slots 22 provide for iiow from the interior of the tube to the space surrounding it, or in the reverse direction, as localized instantaneous pressure conditions necessitate. The exhaust gases from the engine enter the mufflerA under periodically varying pressure conditions, and emerge therefrom silently with pressure variations materially reduced in extent. Because the tube I C has no obstructions within it, the muiiier does not build up a material back pressure. In fact, we ilnd by tests that our mufiler creates substantially no more back-pressure than ds a plain tube of equal length. The silencing action we believe to be due to the flow of gases back and forth through the restricted openings 22.

In the prior patent of Q. G. Noblitt, No. 1.972.065, there is shown a muiiier somewhat similar to that above described, the chief difference between the munier of this application and the mumer of such earlier application, exoept for certain details of construction, being in the presence of the partitions 2li in the muiiler above described. We have found that the presence of the partitions 28 veri,1 materially increases the silencing action of the mumer.

Qur invention is not limited to the specific arrangement so far described and illustrated in -and in alinement with each other.

In the mun'ier illustrated in Figs. 1 and 2, the two halves of the casing are secured to each other and to the center partition i1 by forming the casing-halves Il with annular nanges 3i! which receive the partition I1 between them. After assembly, the three parts are secured together by seam-welding along the circumference of the nanges l! and the partition I1. 'This same method of assembly may be used with the munier In the muiiier illustrated in Figs. 'I and 9, the two halves I5 of the mulder-casing are buttwelded together, the central partition I1 being eliminated and its function being performed by two partitions 3i each of which is secured in 5 place in its associated casing-half l5 at a distance from the large end of such casing-half. The two partitions 3| fit substantially tightly within the mufiier casing and about the inner ends of the two tube-halves I6 in order to prevent gas-ilow from one side of either partition to the other side except through the tube. In the assembled muiller, the two partitions 3| define an expansion chamber having an inlet open ing through one of the two tube-halves I6 and 15 an outlet opening through the other. We have found that such an expansion chamber located near the center, in spite of the enlargement and contraction which it provides in the gas passage, does not produce any appreciable increase in back 50 pressure.

It will be noted that as a result of the manner in which the openings 22 in the tube I6 are shown as formed the gases passing through the muflier from inlet to outlet thereof will flow through gs such openings more readily in one direction than the other. That is, if the tube IB is disposed so that the louvers 2| slope outwardly in the general direction of gas-flow through the muiiier, gases can pass outwardly through the openings I2 30 with but a slight change of direction and will flow from the tube to the space surrounding it more readily than they will flow in the reverse direction. In the claims we have described such an arrangement as providing openings arranged to open outwardly in the general direction' of gas-flow through the tube, and we mean by that expression to include any opening so arranged that the direction of outward gas-flow through it has a substantial component in the direction of o gas-flow through the tube. On the other hand, and for the same reason, if the tube IB is disposed in such a way that the louvers 2| slope inwardly in the general direction of gas ow through the muilier, the gases will pass into the tube more 5 readily than they will pass out into the surrounding space. In the claims we have described the openings provided by the louvers so disposed as 'opening inwardly in the general direction of gasflow through the tube. This expression is ino tended to include an opening so arranged that the direction of inward gas-flow through it has a substantial component in the direction of gasflow through the tube.

We find that better silencing of the exhaust can be obtained by arranging some of the louvers so that they slope outwardly in the general direction of gas flow and others so that they slope inwardly. The best and preferred arrangement is that illustrated in the drawings, where each tube- .0 halt I5 is disposed so that its louvers slope outwardly toward the center partition I1. In this arrangement, the gases enter the muiller into a tube the louvers of which are disposed to favor outflow of gases from the tube and leave the muf Il er through a tube having louvers disposed to favor iniiow of the gases. In addition to providing better silencing, the arrangement of louvers just described makes the muiiier reversible if the two tube-halves IB are of the same diameter. 'o Ordinarily, however, it will be found advisable to make the tube-half I8 in the inlet halt oi the mufiler of slightly larger diameter than the other tube-half, as the gases when entering the mufn fier have higher temperature and greater volume than when leaving.

,In all the muiliers herein specifically illustrated sind, described there is but a single tube or gascharge openings. We have found muiliers of thisv shape to have a wide range of application because of the small amount of room theyrequire on one side of such axis.

The practical design of a muffler for use with a given engine is a compromise between cost and silencing eiiiciency, the object being to make the smallest, simplest, and most economical muiiier which will adequately silence the exhaust of that engine. To an extent the size of the muiiler kdepends upon the size of the engine, larger engines generally requiring larger muiilers. A muilier which will produce adequate silencing of the exhaust gases from a large engine will frequently be found satisfactory for use with a smaller engine; but if a smaller muiiler proves satisfactory with the smaller engine, considerations of economy usually demand that such a smaller muiiler be used.

Size, however, is not the only `characteristic of an enginev which may influence muiiier design. Number of lcylinders, speed, bore-and-stroke ratio, compression ratio, valve timing, spark timing, and the length and diameter of the exhaust pipe are other factors which appear to influence the silencing eiiiciency of an exhaust-muiiler. Due to variation in these or other factors, we have found that for two engines of the same number of cylinders, the engine with the smaller piston displacement may require a larger muiiler than the other.

As an example of a muiller found suitable for use with a specific engine, we may mention a mufiier which has proven satisfactory withthe present Ford engine of four cylinders and approximately 200 cubic inches piston displacement. Such a muiiier was 35 inches inlength and 51/ inches in diameter at the center. The tube` i6 in the inlet half of the muiiler was one and seveneighths inches in diameter, and in the outlet half tendency to increase silencing eiiiciency, and a spacing oi' three-eighths, or even one-quarter, oi an inch may be used if desired. The width of the openings 22 we haveV found to be susceptible of comparatively wide variation without materially influencing the silencing efiiciency of the mufiier; but with a width of much less than 0.010 inches the openings are prone to become clogged, while if the width is increased much over 0.040 inches an adverse effect or silencing becomes noticeable.

Because of the large number of factors external to the muffler which infiuence silencing emciency, as well as because the design of a muiiier is in practice a compromise between cost and the degree of silencing desired, we iind that no general rule for determining the size and other characteristics of a muiiier intended for use with a given engine is applicable. most effective way to develop a muiiier for use with a particular engine is to test with that engine a muilier which is known to give satisfactory results with a generally similar engine. If the degree of silencing produced is not all that is de-10 sired, there are two ways in which it may be increased: The number of auxiliary partitions 2l may be increased, or the size of the muiiier may be made larger. There is a practical limit, largely from the standpoint of cost, to the number of l5 auxiliary partitions 28 which may be `used,and we find it seldom worth while to space such partitions less than about two inches apart, especially near the ends of the muiiier. Ii the desired degree orsilencing is not attained by increasing the 20 number of auxiliary partitions, the size of the muiiier may be increased.

If a muiiier, when first tested withan engine, proves adequate to silence the exhaust, the number of auxiliary partitions 2l or the size of the 25 muiiier, or both, may be reduced with a view to lowering the cost of the munler.

As examples of muiiiers suitable for use with engines larger than the Ford engine above referred to, we might mention that a muiiier 42 30A ameter, and had two auxiliary partitions 28. In 40 l both muiiiers just mentioned, the openings in the walls of the tube I6 were approximately 0.025 inches in width and spacedone-half inch apart, as in the case of the Ford munier. We have found width of` opening and spacing of this order to bei generally applicable. i

vTo avoid the creation of excessive back pressure, the tube i0 in theinlet half of the mumer should have a diameter not materially less than that of the exhaust pipe which supplies gases to it. 'I'he tube I6 in the other hal! of the mulder may be somewhat smaller in diameter than the exhaust pipe, as previously indicated.

'Our muiiier is to be distinguished from a muiiler such as is shown in the Mason Patent No. 1,874,326 and which demands for maximum silencing efiiciency that the openings in the center tube be arranged in spaced groups with a section of unperforated tube separating adjacent groups and with a rather definite relation be- 60 tween the lengths of perforated and unperforated tube-portions. To distinguish from such a muffler, we refer in the claims to our center tube as being provided with a continuous series of openings.

We claim as our invention:

1. A silencer for gases, comprising a hollow casing of gradually decreasing diameter from its longitudinal center toward each end, an eccentric gas-passage extending through said casing and adapted to receive gases at one end and disl charge them at the other end, said casing and gas-passage being arranged to provide a space between them, said gas passage being formed with openings to provide restricted communica- 7 The simplest and 5 tion between its interior and said space at a mul# tipllcity oi points along its length, a transverse main partition dividing the space within the.

canna. and one or more transverse auxiliary partitiom on each side oi said main partition dividimthe interior of said casing into a plurality o! chambers. each oi said auxiliary partitions being formed to provide restricted communication be tween the chambers on opposite sides oi it.

3. A silencer for gases, comprising a hollow elsing o! gradually decreasing diameter from its longitudinal center toward each end, an eccentric galfpassage extending through said casing and adapted to receive gases at one end and discharge them at the other end. said casing and gas-passage being arranged to provide a space between them. said gas passage being formed with openings to provide restricted communication between ita interior `and said space at a multiplicity of points along its length, and a plurality oi' transverse partitions dividing the interior oi said casing into a plurality of chambers.

l. A silencer for gases. comprising a hollow easing o! gradually decreasing diameter from its longitudinal center toward each end. a gas-passage extending through said casing and adapted to receive gases at one end and discharge them at the other end, said casing and gas-passage being arranged to provide a space between them. ldd gas e being formed with openings to provide restricted communication between its intsrior and said space at a multiplicity o! points along its length, a `transverse main partition dividing the space within the casing, and one or more transverse auxiliary partitions on each side oi' `laid main partition dividing the interior oi' said casing into a plurality of chambers, each ot said auxiliary partitions being formed to provide restricted communication between the chambers on owoaite sides o! it.

d. A silencer for gases, comprising a hollow casing os gradually decreasing diameter from its lomitudinal center toward each end, an eccentric gas-passage extending through said casing :and adapted to receive gases at one end and discharge them at' the other end. said casing and gaarpassage being arranged to provide a space bevwecnthem. said gas passage being formed with openings to provide restricted communication bee tween its interior and said space at a multiplicity of points along its length, some oi said openings being arranged to open outwardly and others to open inwardly in the general direction oi gas iiow through said gas-passage.

l 5. A silencer for gases, comprising a hollow casing.` a gas extending through said casing and adapted to receive gases at one end and discharge them at the other end, said casing and gal-passage being arranged to provide a space between them, said gas passage being formed with to provide restricted communication betweenits interior and said space at a multiplieity of points along its length, a transverse partition arranged intermediate the length oi said gas-passage and dividing the space around it into two chambers, the openings on one side of said partition being arranged to open outwardiy in the direction of gas-now through the gas-passage and the openings on the other side ot said partition being arranged to open inwardly in the direction ci gas-flow through said pas- 538e.

6. A silencer as set forth in claim 4 with the addition that openings near the inlet end are arranged to open outwardly in the general direction o1' gas-dow through said passage.

7. A silencer as set forth in claim 5 with the addition that openings near the inlet end are arranged to open outwardly in the general direction of gas-flow through said passage.

8. A silencer i or gases, comprising a hollow casing, and a tube extending through said casing and adapted to receive gases at one end and to discharge them at the other end, said 'tube being provided with louvers sloping outwardly away from the ends of the tube, said tube being located eccentrically in said casing.

9. A silencer for gases, comprising a hollow casing, a gas-passage extending through said casing and adapted to receive gases at one end and discharge them at the other end, said passage having a diameter less than that of the casing to provide a space between the walls of the passage and casing, said passage being formed of two generally similar semicircular sheet-metal stampings disposed in opposed relation and having along their longitudinal edges iianges which are secured together to hold the stampings in proper relation, each ci said stampings being provided with a series oi longitudinally spaced, circumferentially extending slits, the material of the stampings being displaced radially along one side of each slit to form a louver providing in the passagewall an opening affording communication between the interior oi the passage and the space within the casing surrounding it.

10. A silencer as set forth in claim 9 with the addition that each of said stampings has an unlouvered longitudinally extending center portion disposed approximately midway between said flanges, said center portion being onset outwardly beyond said louvers.

1l. A silencer as set forth in claim 9 with the addition that each of said stampings has an unlouvered longitudinally extending center portion disposed approximately midway between said flanges.

12. A silencer for gases, comprising a hollow casing, an eccentric tube extending through said casing and adapted to receive gases at one end and to discharge them at the other end, said casing' and gas-passage being arranged to provide a space between them, said tube being provided with louvers sloping outwardly away from the ends of the tube, and a plurality oi transverse bellies opposing longitudinal now oi gases through said casing in said space.

QUINTIN G. NOBLITI".

EARL C. BOOTH.

EDMUND LUDLOW. 

